Nonmuscle myosin II molecules carry out a wide variety of functions within cells. There are three nonmuscle myosin II genes. We have studied the strain dependence of the ADP release mechanism in nonmuscle myosin IIA and IIB using a solution kinetic approach. The results show that both positive strains accelerate the rate of ADP release whereas negative strain markedly lowers the rate. These results suggest that these myosins, and particularly nonmuscle myosin IIB, are ideally suited to act as tension bearers in cells. We are now using optical trapping nanometry to extend these studies. In addition we have collaborated with another group to examine the ADP-dependent change in lever arm position of nonmuscle myosins IIA and IIB.